1. Field of the Invention
The invention concerns a device for adjusting the tilting resistance of a chair seat, on its own, or a chair body with seat and backrest. This adjustment should be performed in connection with a chair seat which can be moved in the longitudinal direction (or a backrest which is movable in the height direction), the seat being tiltably attached on a base column via a horizontal shaft provided across the chair, wherein tilting resistance and springing are determined by two spring elements, one spring being compressed by tilting in one direction and the other spring being compressed by tilting in the opposite direction, and wherein the spring force is adjustable. An embodiment where the distance between the chair seat's tilting axis and spring element is altered is disclosed, e.g., in applicant's NO patent no. 160 406.
2. The Prior Art
There are previously known chairs, e.g., office chairs, of the above-mentioned type. In these chairs, between the seat and the chair frame there are provided two springs whose spring force can be varied by means of screw devices for separate adjustment of each spring. If the chair frequently changes owner, such a constant alteration of the spring force or the springs' position is difficult to work out, time-consuming and tiresome.
If the chair is used by several different people, i.e., people of different build and weight, each person will have to adjust the springs separately and individually in order to obtain optimum sitting comfort. It has therefore been a requirement to produce a setting or adjusting mechanism for the tilting resistance in a chair seat or chair body, where adjustment can be performed without the need for the user to think or do anything about it. Tall people who require a deep chair seat place a greater load on the tilting resistance than small people, since they are both heavier and taller and create a greater weight moment. Small people who will like a short seat place a smaller load on the tilting resistance both since they are light and since they create a smaller weight moment.
The invention is intended for use in chairs where the seat and possibly the chair back are adjustable in order to adapt the chair's dimensions to different people's size. When the chair seat is pushed forwards and backwards in its longitudinal direction (or the backrest in its height direction), this moves both the tilting resistance means away from and closer to the seat's or the chair body's tilting point respectively. The result of this is that people who are tall and prefer a deep seat/high backrest and adjust the chair accordingly will automatically create greater (harder) tilting resistances both for forward tilt and backward tilt. Similarly, a short person who wishes a short seat/low backrest and adjusts the chair accordingly automatically creates less (weaker) tilting resistances.
The object of the invention is therefore to permit an automatic adaptation of the tilting resistance in such chairs with chair seats which are adjustable in the longitudinal direction, and/or backrests which are adjustable in the height direction.
With such adjustable chairs, however, the situation may still arise where individuals require an adjustment beyond this normal relationship, e.g. a tall person who is very light. Thus it is a further object of the invention to provide a possibility for such a special adjustment, such as weak tilting resistance even though the seat is set in the deep position. The term "normal relationship" should be understood to mean that the chair's functions are arranged so that they move simultaneously in a certain relationship to one another in order to be able to provide satisfactory conditions for different body sizes.
In order to prevent the special setting from being disadvantageous for the next user of the chair, the invention has been implemented in such a manner that when the seat depth is adjusted, special settings automatically return to the normal relationship between the functions.